JP7309726B2 - sealing material - Google Patents

Description

The present invention relates to sealing materials.

Conventionally, sealing materials such as O-rings used in semiconductor manufacturing equipment, semiconductor transfer equipment, liquid crystal manufacturing equipment, vacuum equipment, etc. are required to have plasma resistance, heat resistance, cleanliness, chemical resistance, and the like. Fluororubber is often used as the sealing material.

In general, rubber materials tend to adhere to the metal surfaces to be sealed, and therefore problems such as hindrance to normal operation of devices that are frequently opened and closed are likely to occur. In addition, during maintenance, the sealing material adheres to the metal surface so strongly that it cannot be peeled off, and if the sealing material is forcibly removed, the rubber dust rubs off, causing problems such as malfunction of the device. Such a problem of adhesion to metal surfaces also occurs in sealing materials made of fluororubber, which has a low surface energy. The sticking problem has become prominent.

Therefore, in recent years, efforts have been actively made to develop sealing materials that are difficult to adhere to metal surfaces, that is, have excellent non-adherence to metal surfaces. For example, in Patent Document 1, a fluororubber molded article having a fluorinated surface is disclosed, in which the atomic number ratio of [oxygen atoms/fluorine atoms] and the number of bonds of [C-H bonds/C- _F2 bonds] on the surface The fluororubber molded product, which is characterized in that the ratio is each a predetermined value or less, and that the leak amount after 3 minutes from the start of the helium leak test is a predetermined value or less, is excellent in non-adherence to the metal surface, and moderately It is disclosed that the flexibility is imparted and excellent sealability can also be exhibited.

JP 2008-138107 A

However, there is still room for improvement in the non-adhesiveness to metal surfaces of the above-mentioned conventional sealing materials made of fluororubber moldings.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a sealing material that is excellent in non-adherence to metal surfaces.

The present inventors have made intensive studies to achieve the above object. Then, the present inventors crosslinked a crosslinkable rubber composition containing a binary fluororubber, a carbon material containing carbon nanotubes, and a polyol crosslinking agent, and in contact with a metal surface, a predetermined The present inventors have found that a sealing material made of a cross-linked rubber having a fixed strength to the metal surface after being heated under certain conditions is excellent in non-sticking to the metal surface, and completed the present invention.

That is, an object of the present invention is to advantageously solve the above-mentioned problems. A crosslinkable rubber composition comprising a rubber, a carbon material, and a polyol crosslinking agent is crosslinked, the carbon material containing carbon nanotubes, and after being heated at 250° C. for 70 hours in contact with a metal surface. The adhesion force of the rubber crosslinked product to the metal surface is 2 N or less. Thus, a crosslinkable rubber composition containing a binary fluororubber, a carbon material containing carbon nanotubes, and a polyol crosslinking agent is crosslinked, and heated under predetermined conditions while in contact with a metal surface. A sealing material made of a cross-linked rubber having a fixing force to the metal surface after being cured is equal to or less than the predetermined value can exhibit excellent non-sticking property to the metal surface.
In the present invention, the "fixing force of the crosslinked rubber to the metal surface after being heated at 250°C for 70 hours in contact with the metal surface" is determined by the method described in the Examples of the present specification. can ask.

Here, the ratio Cs/Ca of the carbon material concentration Cs on the surface of the crosslinked rubber product to the average carbon material concentration Ca in the rubber crosslinked product is preferably 0.5 or more. If the ratio Cs/Ca of the concentration Cs of the carbon material on the surface of the crosslinked rubber product to the average concentration Ca of the carbon material in the crosslinked rubber product is equal to or greater than the predetermined value, the non-sticking property of the sealing material to the metal surface is improved. can be further increased.
In the present invention, the "ratio Cs/Ca between the carbon material concentration Cs on the surface of the crosslinked rubber product and the average carbon material concentration Ca in the rubber crosslinked product" is determined by the method described in the examples of the present specification. can be obtained by

Further, the ratio Cs/Ca of the carbon material concentration Cs on the surface of the crosslinked rubber product to the average carbon material concentration Ca in the rubber crosslinked product is preferably more than 1 and 8 or less. If the ratio Cs/Ca of the carbon material concentration Cs on the surface of the crosslinked rubber product to the average carbon material concentration Ca in the rubber crosslinked product is within the predetermined range, the strength of the sealing material is sufficiently high. At the same time, the non-adherence of the sealing material to the metal surface can be further enhanced.

Furthermore, the sealing material of the present invention is usually used in an environment where it is in close contact with a metal surface.

Further, in the sealing material of the present invention, the binary fluororubber is a vinylidene fluoride-hexafluoropropylene copolymer, and the fluorine content in the vinylidene fluoride-hexafluoropropylene copolymer is 65% by mass or more. It is preferably 70% by mass or less. If the binary fluororubber is a vinylidene fluoride-hexafluoropropylene copolymer and the fluorine content in the vinylidene fluoride-hexafluoropropylene copolymer is within the predetermined range, the metal of the sealing material The non-sticking property to the surface can be further enhanced.

Further, in the sealing material of the present invention, the carbon material contains carbon black, and the content of the carbon black in the crosslinkable rubber composition is 5 parts by mass or more with respect to 100 parts by mass of the binary fluororubber. It is preferably 40 parts by mass or less. When the carbon material contains carbon black, and the content of the carbon black in the crosslinkable rubber composition is within the above-described predetermined range, the obtained sealing material can have a sufficiently high sealing property and can be sealed. The compression set resistance of the material can be increased.

Further, in the sealing material of the present invention, it is preferable that the surface area S of the carbon material contained in the rubber crosslinked product is 5 (m ² /g) or more. If the surface area S is within the above range, the non-adherence of the sealing material to the metal surface can be further enhanced.
Here, in the present invention, the "surface area S of the carbon material contained in the crosslinked rubber" can be obtained by the following calculation method. That is, when the rubber crosslinked product contains carbon materials C ₁ to C _n (C ₁ to C _n are different carbon materials; n is an integer of 1 or more), the BET specific surface areas of the carbon materials C ₁ to C _n are S ₁ to S _n (m ² /g), and the contents of the carbon materials C ₁ to C _n in the total amount A (g) of the crosslinked rubber are R ₁ to R _n (g), respectively. The surface area S of the carbon material contained in the object can be calculated by the following formula (1). In the present invention, the "BET specific surface area" refers to the nitrogen adsorption specific surface area measured using the BET method.
S=Σ[S _i ×(R _i /A)](m ² /g) [i is an integer of 1 or more and n or less] (1)
However, for example, when the BET specific surface area S _i (m ² /g) of each carbon material C _i and/or the content R _i (g) in the crosslinked rubber is unknown, the carbon contained in the crosslinked rubber Assuming that there is only one material (C ₁ ), S ₁ (m ² /g) and R ₁ (g) obtained by the following method are applied to the above formula (1) to calculate S can also That is, the rubber crosslinked product is heated in a heating furnace to 600°C under a nitrogen atmosphere, the heating furnace is cooled to 400°C, then switched to an air or oxygen atmosphere, heated to an arbitrary temperature, and carbon generated by thermal decomposition A BET specific surface area S ₁ (m ² /g) can be measured using a sample of the carbon material C ₁ obtained by removing the residual residue. Also, the content R ₁ (g) of the carbon material C ₁ in the crosslinked rubber can be measured according to JIS K6226-2:2003.

Furthermore, in the sealing material of the present invention, the carbon nanotubes preferably include single-walled carbon nanotubes. If the carbon nanotubes include single-walled carbon nanotubes, the non-adherence of the sealing material to the metal surface can be further enhanced.

Further, in the sealing material of the present invention, the content of the carbon nanotubes in the crosslinkable rubber composition is 0.1 parts by mass or more and 4 parts by mass or less with respect to 100 parts by mass of the binary fluororubber. is preferred. If the content of the carbon nanotubes in the crosslinkable rubber composition is within the above-described predetermined range, the sealing material will not stick to the metal surface while ensuring sufficiently high compression set resistance of the sealing material. can be further increased.

Further, in the sealing material of the present invention, the polyol cross-linking agent is preferably a polyhydroxyaromatic compound. If the polyol cross-linking agent is a polyhydroxyaromatic compound, the compression set resistance of the sealing material can be enhanced.

Further, in the sealing material of the present invention, the content of the polyhydroxyaromatic compound in the crosslinkable rubber composition is preferably 10 parts by mass or less with respect to 100 parts by mass of the binary fluororubber. When the content of the polyhydroxyaromatic compound in the crosslinkable rubber composition is equal to or less than the predetermined amount, the compression set resistance of the sealing material can be further enhanced.

Furthermore, in the sealing material of the present invention, it is preferable that the crosslinkable rubber composition further contains a crosslinking accelerator. If the crosslinkable rubber composition further contains a crosslinking accelerator, the compression set resistance of the sealing material can be enhanced.

Further, in the sealing material of the present invention, the cross-linking accelerator contains at least one selected from the group consisting of ammonium salts, phosphonium salts, and amine compounds, and the cross-linking accelerator in the cross-linkable rubber composition The content is preferably 0.1 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the binary fluororubber. The cross-linking accelerator contains at least one selected from the group consisting of ammonium salts, phosphonium salts, and amine compounds, and the content of the cross-linking accelerator in the cross-linkable rubber composition is within the predetermined range. If there is, the compression set resistance of the sealing material can be further enhanced.

Furthermore, in the sealing material of the present invention, the crosslinkable rubber composition preferably further contains an acid acceptor. If the crosslinkable rubber composition further contains an acid-accepting agent, the non-sticking property and compression set resistance of the sealing material to the metal surface can be enhanced.

Further, in the sealing material of the present invention, the acid acceptor preferably contains magnesium oxide and calcium hydroxide. If the acid acceptor contains magnesium oxide and calcium hydroxide, the compression set resistance of the sealing material can be further enhanced.

Further, in the sealing material of the present invention, the surface resistivity of the crosslinked rubber is 1×10 ⁸ Ω/sq. The following are preferable. When the surface resistivity of the crosslinked rubber is not more than the predetermined value, the sealing material is excellent in conductivity and can satisfactorily prevent obstacles caused by static electricity such as adhesion of foreign matter.
In addition, in the present invention, the "surface resistivity of the crosslinked rubber" can be measured by the method described in the examples of the present specification.

In the sealing material of the present invention, the compression set of the crosslinked rubber after being heated at 250° C. for 70 hours is preferably 80% or less. If the compression set rate of the crosslinked rubber after being heated at 250° C. for 70 hours is not more than the predetermined value, the sealing material is excellent in compression set resistance, and thus maintains good sealing properties over a long period of time. be able to.
In the present invention, "the compression set rate of the crosslinked rubber after being heated at 250°C for 70 hours" can be measured by the method described in the Examples of the present specification.

ADVANTAGE OF THE INVENTION According to this invention, the sealing material excellent in non-adherence with respect to the metal surface can be provided.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail.

(Seal material)
The sealing material of the present invention is obtained by cross-linking a cross-linkable rubber composition containing a binary fluororubber, a carbon material containing carbon nanotubes, and a polyol cross-linking agent, and is in contact with a metal surface under predetermined conditions. It is characterized by being made of a rubber cross-linked product having a fixing force to the metal surface after being heated under the environment of a predetermined value or less. Such a sealing material can exhibit excellent non-adherence to metal surfaces.

Here, the reason why the sealing material of the present invention can exhibit excellent non-adhesiveness to the metal surface is not clear, but due to the radical scavenging effect of the carbon material containing the carbon nanotube, the binary fluorine It is presumed that the formation of chemical bonds between the metal surface and the deteriorated binary fluororubber was suppressed because the heat deterioration of the rubber was suppressed.

The use of the sealing material of the present invention is not particularly limited, but usually the sealing material of the present invention is used in an environment in which it is in close contact with a metal surface. Specifically, the sealing material of the present invention can be favorably used as a sealing material for use in semiconductor manufacturing equipment, semiconductor transport equipment, liquid crystal manufacturing equipment, vacuum equipment, and the like. Further, even if the sealing material of the present invention is used in an environment in which it is in close contact with a metal surface, it is difficult to adhere to the metal surface, so it has a long life and is excellent in reusability. Furthermore, since the sealing material of the present invention does not adhere easily to the metal surface and can be easily peeled off from the metal surface, it is possible to shorten the work time for part replacement and the like. In addition, since the sealing material of the present invention is difficult to adhere to the metal surface and the base material is unlikely to break when the sealing material is peeled off from the metal surface, part of the rubber cross-linked product derived from the sealing material remains on the metal surface. It is possible to satisfactorily prevent contamination from occurring. Therefore, devices, equipment, etc. to which the sealing material of the present invention is attached are excellent in maintainability.
In addition, when the sealing material of the present invention is used in a movable part that rotates, reciprocates, and repeatedly attaches and detaches in various devices, the sealing material adheres to the metal surface of the movable part, resulting in operational problems. is unlikely to occur. Therefore, by using the sealing material of the present invention, it is possible to stably control the above-described movable portion.

The sealing material of the present invention can have any shape depending on the application. Further, the sealing materials of the present invention are specifically sealing materials such as O-rings, packings, and gaskets.

<Rubber cross-linked product>
The cross-linked rubber used in the sealing material of the present invention is obtained by cross-linking a cross-linkable rubber composition containing a binary fluororubber, a carbon material containing carbon nanotubes, and a polyol cross-linking agent. Further, the crosslinked rubber product has a fixing force to the metal surface after being heated under predetermined conditions while being in contact with the metal surface, and has a predetermined value or less.

<<Crosslinkable Rubber Composition>>
A crosslinkable rubber composition is a rubber composition that can be crosslinked, and is used when producing the above-described crosslinked rubber product. The crosslinkable rubber composition includes a binary fluororubber, a carbon material containing carbon nanotubes, and a polyol crosslinker. In addition to the above components, the crosslinkable rubber composition may contain compounding agents commonly used in the field of rubber processing.

[Binary fluororubber]
A binary fluororubber is a rubber containing a structural unit derived from a fluorine-containing monomer and composed of a binary copolymer. By including the binary fluororubber in the crosslinkable composition, it is possible to obtain a rubber crosslinked product and a sealing material having good heat resistance and compression set resistance.
Here, specific examples of binary fluororubbers include tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, tetrafluoro Examples include ethylene-propylene copolymers. Among them, it is preferable to use a vinylidene fluoride-hexafluoropropylene copolymer from the viewpoint of enhancing the non-adherence of the sealing material to the metal surface.

When a vinylidene fluoride-hexafluoropropylene copolymer is used as the binary fluororubber, the fluorine content in the vinylidene fluoride-hexafluoropropylene copolymer is 65% by mass or more and 70% by mass or less. is preferred. If the fluorine content in the vinylidene fluoride-hexafluoropropylene copolymer is within the above-specified range, the non-sticking property of the sealing material to the metal surface can be further enhanced.

Commercially available binary fluororubbers include "Viton A200", "VITON A500", "Viton A700", "Viton AHV", "Viton AL300", and "Viton AL600" (vinylidene fluoro rubber) manufactured by Chemours. Ride-Hexafluoropropylene copolymer), etc., and "DAI-EL G-701", "DAI-EL G-702", "DAI-EL G-716", "DAI-EL G-751", "DAI-EL G-755" manufactured by Daikin Industries, Ltd. ”, Sumitomo 3M’s “Dynion FC-2145”, “Dynion FC-2230”, “FC-2178”, etc., and Solvay’s “Technoflon N215/U”, “Technoflon N535”, “ Technoflon N935", "Technoflon N60HS", "Technoflon N90HS" and the like can be preferably used.

[Carbon material]
Carbon materials used in the crosslinkable rubber composition include carbon nanotubes, and optionally other carbon materials other than carbon nanotubes.

-carbon nanotube-
Carbon nanotubes (CNTs) are not particularly limited, and single-walled carbon nanotubes and/or multi-walled carbon nanotubes can be used. CNTs are preferably single-walled to five-walled carbon nanotubes, Single-walled carbon nanotubes are more preferred. This is because the smaller the number of carbon nanotube layers, the better the properties of the crosslinked rubber and the sealing material, such as non-adhesiveness to the metal surface, even if the blending amount is small.

The average diameter of the carbon nanotubes is preferably 1 nm or more, preferably 60 nm or less, more preferably 30 nm or less, and even more preferably 10 nm or less. When the average diameter of the CNTs is 1 nm or more, the dispersibility of the CNTs can be enhanced, and properties such as non-adherence to metal surfaces can be stably imparted to the crosslinked rubber and the sealing material. Moreover, if the average diameter of the CNTs is 60 nm or less, it is possible to efficiently impart properties such as non-sticking properties to the metal surface to the crosslinked rubber and the sealing material even when the amount of the CNTs is small.
In the present invention, the "average diameter of carbon nanotubes" is obtained by measuring the diameter (outer diameter) of, for example, 100 CNTs on a transmission electron microscope (TEM) image and calculating the number average value. can ask.

In addition, for carbon nanotubes, the ratio (3σ) of the value (3σ) obtained by multiplying the standard deviation of the diameter (σ: sample standard deviation) by 3 to the average diameter (Av) (3σ/Av) is more than 0.20 and less than 0.60. of CNTs, more preferably 3σ/Av of more than 0.25, and even more preferably 3σ/Av of more than 0.40. Using CNTs with a 3σ/Av of more than 0.20 and less than 0.60 can further improve the performance of the rubber crosslinked product and the sealing material.
The average diameter (Av) and standard deviation (σ) of CNTs may be adjusted by changing the CNT production method and production conditions, or by combining multiple types of CNTs obtained by different production methods. You may

As the carbon nanotube, the diameter measured as described above is plotted on the horizontal axis and the frequency is plotted on the vertical axis, and when Gaussian approximation is performed, a normal distribution is usually used.

In addition, the average length of the carbon nanotubes is preferably 10 μm or more, more preferably 50 μm or more, even more preferably 80 μm or more, preferably 800 μm or less, and 700 μm or less. is more preferable, and 600 μm or less is even more preferable. If the average length of the CNTs is 10 μm or more, a conductive path can be formed in the crosslinked rubber and the sealing material with a small amount, and the dispersibility of the CNTs can be improved. And if the average length of CNT is 800 micrometers or less, the electroconductivity of a rubber crosslinked material and a sealing material can be stabilized. Therefore, if the average length of CNTs is within the above range, the surface resistivity of the crosslinked rubber and sealing material can be sufficiently reduced.
In the present invention, the average length of the "carbon nanotube" is obtained by measuring the length of 100 CNTs on a scanning electron microscope (SEM) image and calculating the number average value. can be done.

In addition, the carbon nanotubes preferably have a BET specific surface area of 200 m ² /g or more, more preferably 400 m ² /g or more, even more preferably 600 m ² /g or more, and 2000 m ² /g. It is preferably 1800 m ² /g or less, more preferably 1600 m ² /g or less. If the BET specific surface area of the carbon nanotubes is 200 m ² /g or more, the dispersibility of the carbon nanotubes can be enhanced, and properties such as electrical conductivity of the crosslinked rubber and the sealing material can be sufficiently enhanced with a small compounding amount. Further, if the BET specific surface area of the carbon nanotube is 2000 m ² /g or less, the properties of the crosslinked rubber and the sealing material such as non-sticking property to the metal surface can be stabilized.

In addition, the carbon nanotubes preferably show an upward convex shape in the t-plot obtained from the adsorption isotherm. The "t-plot" can be obtained by converting the relative pressure to the average thickness t (nm) of the nitrogen gas adsorption layer in the carbon nanotube adsorption isotherm measured by the nitrogen gas adsorption method. That is, the average thickness t of the nitrogen gas adsorption layer corresponding to the relative pressure is obtained from a known standard isotherm obtained by plotting the average thickness t of the nitrogen gas adsorption layer against the relative pressure P/P0, and the above conversion is performed. gives a t-plot of carbon nanotubes (t-plot method by de Boer et al.).

Here, the growth of a nitrogen gas adsorption layer on a substance having pores on its surface is classified into the following processes (1) to (3). Then, the slope of the t-plot changes due to the following processes (1) to (3).
(1) Formation of a monomolecular adsorption layer of nitrogen molecules on the entire surface (2) Formation of a multimolecular adsorption layer and subsequent capillary condensation filling process within the pores (3) Posterior pores filled with nitrogen Formation process of polymolecular adsorption layer on non-porous surface

Then, the t-plot showing an upwardly convex shape is located on a straight line passing through the origin in a region where the average thickness t of the nitrogen gas adsorption layer is small, whereas when t becomes large, the plot is on the straight line. position shifted downward from A carbon nanotube having such a t-plot shape has a large ratio of the internal specific surface area to the total specific surface area of the carbon nanotube, indicating that many openings are formed in the carbon nanotube.

The inflection point of the t-plot of carbon nanotubes is preferably in the range satisfying 0.2 ≤ t (nm) ≤ 1.5, and is in the range of 0.45 ≤ t (nm) ≤ 1.5 It is more preferable to be in the range of 0.55≦t(nm)≦1.0. If the inflection point of the t-plot of the carbon nanotubes is within such a range, the dispersibility of the carbon nanotubes can be enhanced, and properties such as the non-adherence of the crosslinked rubber and the sealing material to the metal surface can be enhanced with a small amount. . Specifically, if the value of the inflection point is less than 0.2, the carbon nanotubes tend to agglomerate, and the dispersibility decreases. There is a risk that the performance will decrease.
The "position of the bending point" is the intersection of the approximate straight line A in the process (1) described above and the approximate straight line B in the process (3) described above.

Furthermore, the carbon nanotubes preferably have a ratio (S2/S1) of internal specific surface area S2 to total specific surface area S1 obtained from t-plot of 0.05 or more and 0.30 or less. If the value of S2/S1 of the carbon nanotubes is within such a range, the dispersibility of the carbon nanotubes can be enhanced, and properties such as non-adhesion of the crosslinked rubber and sealing material to the metal surface can be enhanced with a small amount.
Here, the total specific surface area S1 and internal specific surface area S2 of the carbon nanotube can be determined from the t-plot. Specifically, first, the total specific surface area S1 can be obtained from the slope of the approximate straight line in process (1), and the external specific surface area S3 can be obtained from the slope of the approximate straight line in process (3). By subtracting the external specific surface area S3 from the total specific surface area S1, the internal specific surface area S2 can be calculated.

By the way, the measurement of the adsorption isotherm of the carbon nanotube, the preparation of the t-plot, and the calculation of the total specific surface area S1 and the internal specific surface area S2 based on the analysis of the t-plot can be performed, for example, by the commercially available measurement device "BELSORP (registered trademark)-mini” (manufactured by Nippon Bell Co., Ltd.).

Furthermore, carbon nanotubes that can be suitably used in the present invention preferably have a radial breathing mode (RBM) peak when evaluated using Raman spectroscopy. Note that RBM does not exist in the Raman spectrum of only multi-walled carbon nanotubes with three or more layers.

CNTs can be produced by known CNT synthesis methods such as an arc discharge method, a laser ablation method, and a chemical vapor deposition method (CVD method), without any particular limitation. Specifically, CNTs are synthesized, for example, by supplying a raw material compound and a carrier gas onto a substrate having a catalyst layer for producing carbon nanotubes on the surface, and synthesizing CNTs by chemical vapor deposition (CVD). In addition, a method of dramatically improving the catalytic activity of the catalyst layer by allowing a trace amount of oxidizing agent (catalyst activating substance) to exist in the system (super-growth method; see International Publication No. 2006/011655). , can be efficiently manufactured. In addition, below, the carbon nanotube obtained by the super growth method may be called "SGCNT."

The content of CNTs to be blended in the crosslinkable rubber composition is preferably 0.1 parts by mass or more, and 0.2 parts by mass or more with respect to 100 parts by mass of the binary fluororubber described above. more preferably 0.4 parts by mass or more, still more preferably 0.5 parts by mass or more, preferably 4 parts by mass or less, and preferably 3 parts by mass or less It is more preferably 2 parts by mass or less, even more preferably 1.5 parts by mass or less, and even more preferably 1 part by mass or less. When the CNT content is at least the above lower limit, properties such as non-adherence to metal surfaces of the crosslinked rubber can be enhanced. Further, if the CNT content is equal to or less than the above upper limit, the dispersibility of the CNTs is lowered, and it is possible to suppress unevenness in properties such as non-adherence to the metal surface of the crosslinked rubber product. Therefore, if the CNT content is within the predetermined range, the non-adherence of the sealing material to the metal surface can be further enhanced. Further, if the content of CNTs in the crosslinkable rubber composition is equal to or less than the above upper limit, sufficiently high resistance to compression set of the obtained crosslinked rubber and sealing material can be ensured.

－Other carbon materials－
Carbon materials other than carbon nanotubes are not particularly limited, and known carbon materials can be used. Specifically, particulate carbon materials, fibrous carbon materials, and the like can be used as other carbon materials.
The particulate carbon material is not particularly limited, and examples thereof include graphite such as artificial graphite, flake graphite, exfoliated graphite, natural graphite, acid-treated graphite, expandable graphite, and expanded graphite; carbon black; can be used. In addition, the fibrous carbon material is not particularly limited, and for example, fibrous carbon nanostructures other than CNTs and fibrous carbon materials other than fibrous carbon nanostructures can be used.

As the other carbon material, it is preferable to use a particulate carbon material, and it is particularly preferable to use carbon black. This is because if carbon black is used as another carbon material, it is possible to impart appropriate strength to the crosslinked rubber and the sealing material, and to enhance the resistance to compression set of the crosslinked rubber and the sealing material.
The content of carbon black in the crosslinkable rubber composition is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and 15 parts by mass with respect to 100 parts by mass of the binary fluororubber. parts by mass or more, more preferably 20 parts by mass or more, preferably 40 parts by mass or less, more preferably 35 parts by mass or less, and further preferably 30 parts by mass or less. preferable. When the content of carbon black in the crosslinkable rubber composition is at least the above lower limit, the compression set resistance of the crosslinked rubber and sealing material can be further enhanced. In addition, if the content of carbon black in the crosslinkable rubber composition is equal to or less than the above upper limit, the flexibility of the crosslinked rubber and the sealing material can be maintained well, and the sealing performance of the sealing material can be sufficiently high. can.

Here, the BET specific surface area of carbon black is preferably 8 m ² /g or more and 100 m ² /g or less. If the BET specific surface area of the carbon black is at least the above lower limit, sufficiently high mechanical strength can be ensured for the resulting crosslinked rubber and sealing material. On the other hand, if the BET specific surface area of the carbon black is equal to or less than the above upper limit, sufficiently high resistance to compression set of the resulting crosslinked rubber and sealing material can be ensured.

[Polyol cross-linking agent]
The polyol cross-linking agent is a component capable of imparting sufficient elasticity to the cross-linked rubber and sealing material obtained by cross-linking the molecules of the binary fluororubber described above, and imparting good resistance to compression set. .

As the polyol cross-linking agent, a polyhydroxy aromatic compound can be preferably used from the viewpoint of enhancing the resistance to compression set of the cross-linked rubber and the sealing material. The polyhydroxyaromatic compound is not particularly limited, and examples thereof include 2,2-bis(4-hydroxyphenyl)propane (bisphenol A) and 2,2-bis(4-hydroxyphenyl)perfluoropropane (bisphenol AF). , resorcin, 1,3-dihydroxybenzene, 1,7-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 4,4′-dihydroxydiphenyl, 4,4′-dihydroxystilbene, 2,6 -dihydroxyanthracene, hydroquinone, catechol, 2,2-bis(4-hydroxyphenyl)butane, 4,4-bis(4-hydroxyphenyl)valeric acid, 2,2-bis(4-hydroxyphenyl)tetrafluorodichloropropane , 4,4′-dihydroxydiphenyl sulfone, 4,4′-dihydroxydiphenyl ketone, tri(4-hydroxyphenyl)methane, 3,3′,5,5′-tetrachlorobisphenol A, 3,3′,5, 5′-Tetrabromobisphenol A and the like are included. Among them, it is preferable to use bisphenol AF.

The content of the polyhydroxyaromatic compound in the crosslinkable rubber composition is preferably at least 0.1 parts by mass, and at least 0.2 parts by mass with respect to 100 parts by mass of the binary fluororubber described above. more preferably 0.4 parts by mass or more, preferably 10 parts by mass or less, more preferably 6 parts by mass or less, and even more preferably 3 parts by mass or less . When the content of the polyhydroxyaromatic compound in the crosslinkable rubber composition is at least the above lower limit, the compression set resistance of the crosslinked rubber and sealing material can be further enhanced. In addition, if the content of the polyhydroxyaromatic compound in the crosslinkable rubber composition is equal to or less than the above upper limit, the elasticity of the crosslinked rubber and the sealing material is prevented from being impaired due to excessive crosslinking, and the durability of the sealing material is improved. Compression set can be further enhanced.

[Compounding agent]
Compounding agents that are optionally compounded into the crosslinkable rubber composition include known compounding agents such as cross-linking accelerators and acid acceptors.

-Crosslinking accelerator-
Here, the cross-linking accelerator preferably contains at least one selected from the group consisting of ammonium salts, phosphonium salts and amine compounds. When at least one of the above-mentioned predetermined components is used as a cross-linking agent, the cross-linking reaction of the binary fluororubber by the above-described polyol cross-linking agent is promoted, and the compression set resistance of the cross-linked rubber and the sealing material is enhanced. can be done.

Ammonium salts that can be used as crosslinking accelerators include 8-methyl-1,8-diazabicyclo[5,4,0]-7-undecenium chloride, 8-methyl-1,8-diazabicyclo[5, 4,0]-7-undecenium iodide, 8-methyl-1,8-diazabicyclo[5,4,0]-7-undecenium hydroxide, 8-methyl-1,8-diazabicyclo[5 ,4,0]-7-undecenium methyl sulfate, 8-ethyl-1,8-diazabicyclo[5,4,0]-7-undecenium bromide, 8-propyl-1,8-diazabicyclo[5 ,4,0]-7-undecenium bromide, 8-dodecyl-1,8-diazabicyclo[5,4,0]-7-undecenium chloride, 8-dodecyl-1,8-diazabicyclo[5,4 ,0]-7-undecenium hydroxide, 8-eicosyl-1,8-diazabicyclo[5,4,0]-7-undecenium chloride, 8-tetracosyl-1,8-diazabicyclo[5,4 ,0]-7-undecenium chloride, 8-benzyl-1,8-diazabicyclo[5,4,0]-7-undecenium chloride, 8-benzyl-1,8-diazabicyclo[5,4,0 ]-7-undecenium hydroxide, 8-phenethyl-1,8-diazabicyclo[5,4,0]-7-undecenium chloride, 8-(3-phenylpropyl)-1,8-diazabicyclo [ 5,4,0]-7-undecenium chloride and the like. Phosphonium salts include tetrabutylphosphonium chloride, benzyltrimethylphosphonium chloride, benzyltributylphosphonium chloride, tributylallylphosphonium chloride, tributyl-2-methoxypropylphosphonium chloride, benzylphenyl(dimethylamino)phosphonium chloride, and benzyltriphenylphosphonium chloride. chloride and the like. Further, examples of amine compounds include cyclic amines and monofunctional amine compounds.
Among them, phosphonium salts are preferably used, and benzyltriphenylphosphonium chloride is more preferably used, from the viewpoint of further enhancing the compression set resistance of the crosslinked rubber and sealing material.

The content of the crosslinking accelerator in the crosslinkable rubber composition is preferably 0.1 parts by mass or more, and is 0.2 parts by mass or more with respect to 100 parts by mass of the binary fluororubber described above. more preferably 0.3 parts by mass or more, preferably 5 parts by mass or less, more preferably 4 parts by mass or less, and even more preferably 3 parts by mass or less. When the content of the cross-linking accelerator in the cross-linkable rubber composition is at least the above lower limit, the compression set resistance of the cross-linked rubber and sealing material can be further enhanced. Further, if the content of the cross-linking accelerator in the cross-linkable rubber composition is equal to or less than the above upper limit, the elasticity of the cross-linked rubber and the sealing material is prevented from being impaired due to excessive cross-linking. Compression set resistance can be further enhanced.

-acid acceptor-
The acid acceptor is a component capable of absorbing hydrogen fluoride generated by the cross-linking reaction of the binary rubber with the polyol cross-linking agent. Therefore, if the crosslinkable rubber composition contains an acid acceptor, deterioration of the crosslinked rubber due to hydrogen fluoride can be suppressed. As a result, it is possible to satisfactorily prevent the elasticity of the cross-linked rubber product and the sealing material from being impaired, and improve the resistance to compression set of the cross-linked rubber product and the sealing material. Furthermore, the non-adherence of the cross-linked rubber and the sealing material to the metal surface can also be enhanced.

The acid acceptor is not particularly limited and includes magnesium oxide, calcium oxide, zinc oxide, calcium silicate, calcium hydroxide, zinc hydroxide, aluminum hydroxide, hydrotalcite and the like. Among them, it is preferable to use magnesium oxide or calcium hydroxide, and it is more preferable to use them in combination. By using magnesium oxide and calcium hydroxide together as an acid acceptor, it is possible to further improve the non-adherence and compression set resistance of the crosslinked rubber and sealing material to the metal surface.

When magnesium oxide and calcium hydroxide are used together as an acid acceptor, the content of magnesium oxide in the crosslinkable rubber composition is 1 part by mass or more with respect to 100 parts by mass of the above-described binary fluororubber. It is preferably 1.5 parts by mass or more, more preferably 3 parts by mass or more, preferably 5 parts by mass or less, and more preferably 4 parts by mass or less. In addition, the content of calcium hydroxide in the crosslinkable rubber composition is preferably 4 parts by mass or more, more preferably 5 parts by mass or more, with respect to 100 parts by mass of the binary fluororubber described above. It is preferably 6 parts by mass or more, more preferably 10 parts by mass or less, and more preferably 8 parts by mass or less. If the contents of magnesium oxide and calcium hydroxide in the crosslinkable rubber composition are each at least the above lower limits, the non-sticking property and compression set resistance of the crosslinked rubber product and the sealing material to the metal surface can be further enhanced. . Further, if the contents of magnesium oxide and calcium hydroxide in the crosslinkable rubber composition are each equal to or less than the above upper limits, crosslinking can be performed at an appropriate crosslinking rate, and the compression set resistance of the crosslinked rubber and sealing material can be reduced. You can further enhance your sexuality.

[Method for producing crosslinkable rubber composition]
The crosslinkable rubber composition can be prepared by mixing the ingredients described above in a known manner. For example, after performing a mixing step of preparing a mixture by mixing a binary fluororubber and a carbon material containing carbon nanotubes, the mixture, a polyol cross-linking agent, and optional compounding agents are kneaded. By performing the kneading step, the crosslinkable rubber composition can be efficiently prepared.

-Mixing process-
In the mixing step, a mixture is prepared by mixing binary fluororubber and carbon nanotubes as a carbon material.

The mixture of the binary fluororubber and the carbon nanotubes can be prepared using any mixing method capable of dispersing the carbon nanotubes in the binary fluororubber.
For example, carbon nanotubes are added to a rubber dispersion obtained by dissolving or dispersing a binary rubber in a dispersion medium such as an organic solvent, and a known dispersion treatment is performed to obtain a dispersion treatment liquid. Alternatively, the carbon nanotubes are added to an organic solvent or dispersion medium capable of dissolving or dispersing the binary rubber and subjected to dispersion treatment, and the binary rubber is added to the obtained carbon nanotube dispersion and dissolved. Alternatively, a dispersion treatment liquid can be obtained by dispersing.
A mixture of binary rubber and carbon nanotubes can be prepared by removing the organic solvent or dispersion medium from the dispersion treatment liquid thus obtained by a known method.

The distributed processing can be performed using a known distributed processing method. Such a dispersion treatment method is not particularly limited, and examples thereof include an ultrasonic homogenizer, a wet jet mill, a high-speed rotary shearing disperser, and the like.

Then, the dispersion medium is removed from the obtained dispersion treatment liquid to obtain a mixture. As a method for removing the dispersion medium, known methods such as a coagulation method, a casting method, and a drying method can be used.

- Kneading process -
In the kneading step, a crosslinkable rubber composition is obtained by kneading the mixture, the polyol cross-linking agent, and optional compounding agents.
Specifically, the mixture obtained in the mixing step described above further contains a polyol cross-linking agent and optional compounding agents such as a cross-linking accelerator and an acid acceptor, and is kneaded to obtain a cross-linking property. A rubber composition can be obtained. Kneading of the mixture, the polyol cross-linking agent, and any compounding agent can be carried out using, for example, a mixer, a single-screw kneader, a twin-screw kneader, rolls, a pressure kneader, Brabender (registered trademark), an extruder, or the like. can be done.
At the time of kneading, in addition to the components described above, a carbon material other than carbon nanotubes (for example, carbon black) and a binary fluororubber may be added.

<<Method for producing crosslinked rubber (sealing material)>>
A rubber cross-linked product can be produced by cross-linking the cross-linkable rubber composition described above. At this time, the sealing material can be manufactured by shaping the crosslinked rubber into a desired shape. Specifically, the sealing material can be produced by heating a crosslinkable rubber composition to cause a crosslink reaction and fixing the shape of the obtained crosslinked rubber product. In this case, press molding and cross-linking can be performed at the same time, for example, by putting the cross-linkable rubber composition into a mold having a desired shape and heating it. Alternatively, the crosslinkable rubber composition is put into a mold of a desired shape and heated to perform press molding and primary crosslinking at the same time. Secondary cross-linking can also be performed by heating.
Conditions such as the temperature and time of the cross-linking reaction can be appropriately set within a range in which the desired effects of the present invention can be obtained.

<<Physical properties of cross-linked rubber>>
[Adhesive strength to metal surface]
The crosslinked rubber used in the sealing material of the present invention must have a fixing force of 2 N or less to the metal surface after being heated at 250° C. for 70 hours in contact with the metal surface. It is preferably 0.5N or less, more preferably 1N or less, and even more preferably 0.4N or less. If the adhesiveness of the crosslinked rubber to the metal surface is equal to or less than the above upper limit, the sealing material can exhibit excellent non-adhesiveness to the metal surface.

[Surface resistivity]
The surface resistivity of the crosslinked rubber used in the sealing material of the present invention is 1×10 ⁸ to 1×10 ⁵ Ω/sq., which is the electrostatic discharge (ESD) region. Alternatively, 1×10 ⁵ Ω/sq. can be:
The crosslinked rubber has a surface resistivity of 1×10 ⁸ to 1×10 ⁵ Ω/sq. In the case of , even if a charged body comes into contact with the rubber crosslinked product, the charge can be dissipated without causing severe electrostatic discharge. Moreover, when the surface resistivity of the crosslinked rubber is 1×10 ⁵ Ω/sq. In the case of the following, static electricity or the like charged in the rubber crosslinked product can be discharged instantaneously.
When the surface resistivity of the crosslinked rubber is within the above range, the sealing material made of the crosslinked rubber can satisfactorily prevent obstacles caused by static electricity such as adhesion of foreign matter.

[Compression set rate]
Furthermore, the cross-linked rubber used in the sealing material of the present invention preferably has a compression set rate of 80% or less, more preferably 70% or less after being heated at 250° C. for 70 hours. % or less, more preferably 55% or less. If the compression set rate of the crosslinked rubber after heating under the predetermined conditions is equal to or less than the upper limit, the sealing material has excellent compression set resistance, and thus exhibits good sealing performance over a long period of time. can do.

<<Surface Area of Carbon Material Contained in Crosslinked Rubber>>
The surface area S of the carbon material contained in the crosslinked rubber used in the sealing material of the present invention is preferably 5 (m ² /g) or more, more preferably 5.5 (m ² /g) or more. It is preferably 6 (m ² /g) or more, more preferably 25 (m ² /g) or less, and more preferably 15 (m ² /g) or less. If the surface area S of the carbon material contained in the crosslinked rubber is equal to or greater than the above lower limit, the non-sticking property of the sealing material to the metal surface can be further enhanced. On the other hand, if the surface area S of the carbon material contained in the crosslinked rubber is equal to or less than the above upper limit, a sufficiently high compression set resistance of the sealing material can be ensured.
The surface area S of the carbon material contained in the crosslinked rubber can be adjusted by changing the type and content of the carbon material in the crosslinkable rubber composition used to produce the crosslinked rubber. For example, when the content of fibrous carbon nanostructures such as carbon nanotubes with a large BET specific surface area is increased, the value of S can be efficiently increased. On the other hand, even if the content of a carbon material with a small BET specific surface area, for example, a carbon material other than fibrous carbon nanostructures (such as carbon black) is increased, it is difficult to efficiently increase the value of S described above.

<<Ratio Cs/Ca between the concentration Cs of the carbon material on the surface of the crosslinked rubber and the average concentration Ca of the carbon material in the crosslinked rubber>>
The ratio Cs/Ca of the carbon material concentration Cs on the surface of the crosslinked rubber product to the average carbon material concentration Ca in the rubber crosslinked product is preferably 0.5 or more, more preferably greater than 1, and 1 0.5 or more is more preferable, 2 or more is even more preferable, 8 or less is preferable, and 6 or less is more preferable. If the Cs/Ca ratio is 0.5 or more, the resulting crosslinked rubber and sealing material can exhibit even better non-adherence to metal surfaces. On the other hand, if the Cs/Ca ratio is 8 or less, the carbon material is not excessively concentrated on the surface of the crosslinked rubber, and a sufficient amount of the carbon material is also present inside the crosslinked rubber. The material can exhibit sufficient strength.

Here, the value of Cs/Ca, the ratio of the carbon material concentration Cs on the surface of the crosslinked rubber product to the average carbon material concentration Ca in the crosslinked rubber product, is the component in the crosslinkable rubber composition used to produce the crosslinked rubber product. , in particular, can be adjusted by changing the type and content of the carbon material.

The average concentration Ca (% by mass) of the carbon material in the crosslinked rubber generally matches the content ratio (% by mass) of the carbon material in the crosslinkable rubber composition described above. However, for example, when the content ratio (% by mass) of the carbon material in the crosslinkable rubber composition is unknown, the rubber crosslinked product should be analyzed in accordance with the method described in JIS K-6226-2:2003. can measure the average concentration Ca of the carbon material in the crosslinked rubber.

By setting the ratio Cs/Ca of the carbon material concentration Cs on the surface of the crosslinked rubber to the average concentration Ca of the carbon material in the crosslinked rubber to the above-mentioned predetermined value or more, the crosslinked rubber and the sealing material are attached to the metal surface. Although the reason why it is possible to exhibit even better non-sticking property against the above is not clear, it is presumed as follows. That is, by increasing the concentration of the carbon material on the surface of the crosslinked rubber product, the concentration of the binary rubber on the surface of the crosslinked rubber product decreases, and the physical interaction between the metal surface and the crosslinked rubber product can be reduced. Therefore, it is presumed that the adhesion force of the crosslinked rubber to the metal surface can be reduced.

EXAMPLES The present invention will be specifically described below based on examples, but the present invention is not limited to these examples. In the following description, "%" and "parts" representing amounts are based on mass unless otherwise specified.
In the examples and comparative examples, the adhesion force of the crosslinked rubber to the metal surface, the compression set rate, the surface resistivity, the surface area S of the carbon material contained in the crosslinked rubber, and the concentration Cs of the carbon material on the surface of the crosslinked rubber The ratio Cs/Ca to the average concentration Ca of the carbon material in the crosslinked rubber was measured or calculated using the following methods.

<Adhesive force of cross-linked rubber to metal surface>
The crosslinkable rubber composition is press-molded at 160° C. for 20 minutes while applying pressure to 10 MPa using a mold to obtain P-28 (wire diameter 3.5 mm, inner diameter 27.7 mm, A primary crosslinked product press-molded into an O-ring having an outer diameter of 34.7 mm was obtained. Next, the resulting primary crosslinked product was heated in a gear oven at 232° C. for 2 hours for secondary crosslinking. The resulting O-ring-shaped crosslinked rubber sealing material was cut into a semicircular shape (cut in the thickness direction) to obtain a test piece. After wrapping aluminum foil around 1 cm from one end A of the test piece and applying silicone oil to the upper surface of the semicircular shape, the test piece was sandwiched between stainless steel (SUS304) metal plates with a thickness of 1 mm, and the thickness A test body was obtained by compressing 25% in the direction. This specimen was placed in a gear oven at 250° C. and left for 70 hours. After the end of standing, the specimen was taken out from the gear oven, cooled at room temperature, then released from compression, and the upper metal plate (metal plate on the silicone oil side) was removed. After fixing the metal plate with the semicircular O-ring attached, a clip is attached to the aluminum foil wound part of the end A of the test piece, and a mechanical force gauge (FB-20N made by Imada) is clipped. The maximum load (N) measured at that time was taken as the adhesion force of the crosslinked rubber to the metal surface. The smaller the adhesion force of the crosslinked rubber to the metal surface measured by the above method, the more excellent the non-adhesiveness of the crosslinked rubber sealant to the metal surface.

<Compression set rate>
Using a mold, the crosslinkable rubber composition was press-molded at 160° C. for 25 minutes under a pressure of 10 MPa to obtain a cylindrical primary crosslinked product with a diameter of 29 mm and a height of 12.7 mm. Next, the resulting primary crosslinked product was further heated in a gear oven at 232° C. for 2 hours for secondary crosslinking, thereby obtaining a sealing material made of a cylindrical crosslinked rubber product. Then, according to JIS K6262, using the obtained crosslinked rubber material constituting the sealing material, the rubber crosslinked material was compressed by 25% and placed in an environment of 250° C. for 70 hours. It was measured. The smaller the value of the compression set rate of the crosslinked rubber, the more excellent the compression set resistance of the sealing material made of the crosslinked rubber.

<Surface resistivity>
The crosslinkable rubber composition was placed in a mold having a length of 15 cm, a width of 15 cm and a depth of 0.2 cm, and press-molded at 160° C. for 20 minutes under a pressure of 10 MPa to obtain a sheet-like primary cross-linked product. Next, the resulting sheet-like primary cross-linked product was heated in a gear oven at 232° C. for 2 hours for secondary cross-linking to obtain a sheet-like cross-linked rubber sealing material. Using the obtained sealing material as a test piece, a low resistivity meter (manufactured by Mitsubishi Chemical Analytech Co., Ltd., product name "Loresta-GP MCP-T600", applied voltage 90 V, under conditions of temperature 23 ° C. and humidity 50% RH, Using an LSP probe), the surface resistivity of the crosslinked rubber was obtained by measuring the surface resistivity of the central portion within the surface of the test piece. The smaller the surface resistivity of the crosslinked rubber, the more excellent the electrical conductivity of the sealing material made of the crosslinked rubber, and the better the prevention of troubles caused by static electricity such as adhesion of foreign matter.

<Surface area S of carbon material contained in crosslinked rubber>
The surface area S of the carbon material contained in the rubber cross-linked products obtained in Examples and Comparative Examples was calculated by the above-described formula (1).
Note that the mass of the crosslinked rubber product and the mass of the crosslinkable rubber composition used in the preparation of the crosslinked rubber product are the same, and each carbon material C ₁ to C _n in the total amount A (g) of the crosslinked rubber product _{is the content R 1 ' to R n} '(g), respectively.

<Ratio Cs/Ca between the concentration Cs of the carbon material on the surface of the crosslinked rubber and the average concentration Ca of the carbon material in the crosslinked rubber>
By obtaining the carbon material concentration Cs on the surface of the crosslinked rubber and the average carbon material concentration Ca in the crosslinked rubber by the following method, the ratio Cs/Ca of the two was calculated.
<<Concentration Cs of Carbon Material on Surface of Crosslinked Rubber>>
Using the crosslinkable rubber composition, a sheet-shaped crosslinked rubber sealing material obtained in the same manner as in the measurement of the surface resistivity of the molded article was cut into 3 mm squares, and the surface of the crosslinked rubber was up. It was fixed to a carbon double-sided tape so as to be a test piece. The concentration Cs (% by mass) of the carbon material on the surface of the rubber crosslinked product was calculated by analyzing the obtained test piece using an X-ray photoelectron spectroscopy (XPS, manufactured by KRATOS, "AXIS ULTRA DLD") device. . The analysis method and measurement conditions of XPS, and the calculation method of Cs are as follows.
[Analysis method]
Wide scan analysis and narrow scan analysis [measurement conditions]
X-ray source: AlKα monochromator X-ray conditions: 150 W (acceleration voltage 15 kV, current value 10 mA)
Photoelectron capture angle: angle θ90° between sample surface and detector direction
[Measurement condition]
Under the above measurement conditions, wide scan analysis was first performed to confirm the elements present in the crosslinked rubber, and then narrow scan analysis of all detected elements was performed. Next, using an analysis application ("Vision Processing" manufactured by KRATOS), after correcting the peak derived from the carbon material in the carbon 1s orbital to 284.5 eV, the measured peak area of each element was integrated, and the element After correction with another sensitivity coefficient, the element ratio (carbon concentration dC (mass %)) on the surface of the rubber crosslinked product was calculated. Next, the obtained spectrum of the carbon 1s orbital detected at 282 eV or more and 298 eV or less was subjected to waveform separation to calculate the carbon concentration dCs (% by mass) derived from the carbon material in the total carbon. Next, the carbon filler concentration Cs (mass %) was calculated.
Cs = (dC x dCs)/100
<<Average concentration Ca of carbon material in cross-linked rubber product>>
The average concentration Ca of the carbon material in the rubber crosslinked product matches the content ratio (% by mass) of the carbon material in the crosslinkable rubber composition. Therefore, Ca (% by mass) was calculated by the following formula.
Ca = (content of carbon material in crosslinkable rubber composition/amount of all components in crosslinkable rubber composition) x 100

(Example 1-1)
<Carbon nanotubes including single-walled carbon nanotubes>
A carbon nanotube ("ZEONANO SG101" manufactured by Zeon Nanotechnology Co., Ltd.) manufactured by the super-growth method was used as the carbon material _C1 . The carbon nanotubes (arbitrarily referred to as “SGCNTs”) are mainly composed of single-walled CNTs, and when measured with a Raman spectrophotometer, in the low wavenumber region of 100 to 300 cm ⁻¹ , radial breathing characteristic of single-walled CNTs A spectrum of modes (RBM) was observed. The BET specific surface area of SGCNT measured using a BET specific surface area meter (BELSORP (registered trademark)-max, manufactured by Bell Japan Co., Ltd.) was 1347 m ² /g (unopened). Furthermore, the diameter and length of 100 randomly selected SGCNTs were measured using a transmission electron microscope, and the average diameter (Av) of SGCNTs, the standard deviation of the diameter (σ) and the average length were obtained. , the average diameter (Av) is 3.3 nm, the standard deviation (σ) multiplied by 3 (3σ) is 1.9 nm, their ratio (3σ/Av) is 0.58, and the average The length was 500 μm. Furthermore, when the t-plot of SGCNT was measured using “BELSORP (registered trademark)-mini” manufactured by Bell Japan Co., Ltd., the t-plot was curved in an upward convex shape. S2/S1 was 0.09, and the bending point position t was 0.6 nm.

<Preparation of Crosslinkable Rubber Composition>
<<Preparation of mixture>>
100 g of binary fluororubber (Viton A500, manufactured by Chemours, vinylidene fluoride-hexafluoropropylene copolymer, fluorine content: 66% by mass) was added to 900 g of methyl ethyl ketone as an organic solvent, and stirred for 24 hours to form a binary The fluororubber was dissolved.
Next, 4 g of SGCNT as the carbon material _C1 was added to the resulting binary fluororubber solution, and the mixture was stirred for 15 minutes using a stirrer (Labo Solution (registered trademark) manufactured by PRIMIX). Furthermore, using a wet jet mill (L-ES007 manufactured by Yoshida Kikai Kogyo Co., Ltd.), the solution containing SGCNT was subjected to dispersion treatment at 90 MPa. After that, the resulting dispersion treatment liquid was dropped into 4000 g of isopropyl alcohol and solidified to obtain a black solid. The resulting black solid was dried under reduced pressure at 60° C. for 12 hours to obtain a mixture (masterbatch) of binary fluororubber and SGCNT.

<<Kneading>>
Then, using an open roll at 50 ° C., 52 g of the mixture (masterbatch) of 100 g of the binary fluororubber and 4 g of SGCNT, 50 g of the binary fluororubber (manufactured by Chemours, Viton A500), 3 g of magnesium oxide (manufactured by Kyowa Chemical Industry Co., Ltd., trade name "Kyowa Mag 150") and 6 g of calcium hydroxide (manufactured by Omi Chemical Industry Co., Ltd., trade name "Cardic 2000") as an acid acceptor, and a polyol-based cross-linking agent and cross-linking 2.5 g of an accelerator mixture (manufactured by Chemours, trade name "VC-50", a mixture of bisphenol AF/benzyltriphenylphosphonium chloride at a mass ratio of about 4/1) was kneaded, and the roll interval was adjusted to 2 mm. After that, the rubber kneaded product was wound around a roll, and after performing left and right turnover three times each, the sheet was taken out to obtain a crosslinkable rubber composition.
Using a sealing material comprising a rubber crosslinked product obtained by crosslinking the obtained crosslinkable rubber composition, the adhesive strength of the crosslinked rubber product to a metal surface, the surface resistivity, the compression set rate, and the content of the crosslinked rubber product were evaluated. The surface area of the carbon material was measured or calculated. Table 1 shows the results.

(Example 1-2)
During kneading, the addition amount of the above-mentioned mixture (masterbatch) was changed from 52 g to 26 g, and the addition amount of the binary fluororubber (manufactured by Chemours, Viton A500) was changed from 50 g to 75 g. A crosslinkable rubber composition was prepared in the same manner as in 1-1. Then, evaluation was performed in the same manner as in Example 1-1. Table 1 shows the results.

(Example 1-3)
Crosslinking was carried out in the same manner as in Example 1-2, except that 20 g of carbon black (Thermax MT, BET specific surface area: 9.1 m ² /g, manufactured by Cancarb) was further added as carbon material C ₂ during kneading. A flexible rubber composition was prepared. Then, evaluation was performed in the same manner as in Example 1-1. Table 1 shows the results.

(Example 1-4)
During kneading, the amount of the mixture (masterbatch) added was changed from 52 g to 13 g, the amount of binary fluororubber (Viton A500 manufactured by Chemours) was changed from 50 g to 87.5 g, and carbon A crosslinkable rubber composition was prepared in the same manner as in Example 1-1 except that 20 g of carbon black (Thermax MT manufactured by Cancarb, BET specific surface area: 9.1 m ² /g) was further added as material C ₂ . . Then, evaluation was performed in the same manner as in Example 1-1. Table 1 shows the results.

(Comparative Example 1-1)
<Preparation of Crosslinkable Rubber Composition>
<<Kneading>>
Using an open roll at 50 ° C., 100 g of binary fluororubber (Viton A500, manufactured by Chemours) and carbon black (Thermax _MT , manufactured by Cancarb, BET specific surface area: 9.1 m ² / g) 20 g, 3 g of magnesium oxide (manufactured by Kyowa Kagaku Kogyo Co., Ltd., trade name "Kyowa Mag 150") and 6 g of calcium hydroxide (manufactured by Ohmi Kagaku Kogyo Co., Ltd., trade name "Cardic 2000") as an acid acceptor, and a polyol 2.5 g of a mixture of a system cross-linking agent and a cross-linking accelerator (manufactured by Chemours, trade name "VC-50", a mixture of bisphenol AF and benzyltriphenylphosphonium chloride at a mass ratio of about 4/1), After adjusting the gap between rolls to 2 mm, the rubber kneaded product was wound around a roll, turned left and right three times each, and then sheeted out to obtain a crosslinkable rubber composition. Then, evaluation was performed in the same manner as in Example 1-1. Table 1 shows the results.

(Example 2-1)
A crosslinkable rubber composition was prepared in the same manner as in Example 1-1. Using a sealing material composed of a crosslinked rubber obtained by crosslinking the obtained crosslinkable rubber composition, the adhesion force of the crosslinked rubber to the metal surface, the surface resistivity, and the concentration Cs of the carbon material on the surface of the crosslinked rubber were evaluated. and the average concentration Ca of the carbon material in the rubber crosslinked product, the ratio Cs/Ca was measured or calculated. Table 2 shows the results.

(Example 2-2)
A crosslinkable rubber composition was prepared in the same manner as in Example 1-2. Then, evaluation was performed in the same manner as in Example 2-1. Table 2 shows the results.

(Comparative Example 2-1)
A crosslinkable rubber composition was prepared in the same manner as in Comparative Example 1-1, except that the amount of carbon black (Thermax MT manufactured by Cancarb) added during kneading was changed from 20 g to 15 g. Then, evaluation was performed in the same manner as in Example 2-1. Table 2 shows the results.

(Comparative Example 2-2)
A crosslinkable rubber composition was prepared in the same manner as in Comparative Example 1-1 except that the amount of carbon black (Thermax MT manufactured by Cancarb) added during kneading was changed from 20 g to 30 g. Then, evaluation was performed in the same manner as in Example 2-1. Table 2 shows the results.

From Tables 1 and 2, it is obtained by cross-linking a cross-linkable rubber composition containing a binary fluororubber, a carbon material containing carbon nanotubes, and a polyol cross-linking agent, and is in contact with a metal surface. In Examples 1-1 to 1-4 and 2-1 to 2-2, in which a crosslinked rubber having a fixed strength to the metal surface after being heated under conditions of a predetermined value or less is obtained, It can be seen that a sealing material capable of exhibiting excellent non-sticking properties can be provided.
On the other hand, in Comparative Examples 1-1, 2-1 and 2-2 using carbon materials containing no carbon nanotubes, the resulting crosslinked rubber was heated under predetermined conditions while in contact with a metal surface. It is found that the sealing material made of the cross-linked rubber is inferior in non-adhesiveness to the metal surface, because the adhesive force of the rubber to the metal surface exceeds a predetermined value.

ADVANTAGE OF THE INVENTION According to this invention, the sealing material excellent in non-adherence with respect to the metal surface can be provided.

Claims (12)

A sealing material made of a rubber crosslinked product,
The rubber cross-linked product is obtained by cross-linking a cross-linkable rubber composition containing a binary fluororubber, a carbon material, a polyol cross-linking agent , and a cross-linking accelerator ,
The carbon material includes carbon nanotubes,
The content of the carbon nanotubes in the crosslinkable rubber composition is 0.1 parts by mass or more and 4 parts by mass or less with respect to 100 parts by mass of the binary fluororubber,
The polyol cross-linking agent is a polyhydroxy aromatic compound,
The content of the polyhydroxy aromatic compound in the crosslinkable rubber composition is 0.1 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the binary fluororubber,
The cross-linking accelerator contains at least one selected from the group consisting of ammonium salts, phosphonium salts, and amine compounds,
The content of the crosslinking accelerator in the crosslinkable rubber composition is 0.1 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the binary fluororubber,
A sealing material, wherein the adhesive strength of the cross-linked rubber to the metal surface is 2 N or less after being heated at 250° C. for 70 hours while in contact with the metal surface. 2. The sealing material according to claim 1, wherein a ratio Cs/Ca of a carbon material concentration Cs on the surface of said crosslinked rubber product and an average carbon material concentration Ca in said rubber crosslinked product is 0.5 or more. The sealing material according to claim 2, wherein the ratio Cs/Ca of the carbon material concentration Cs on the surface of the crosslinked rubber product to the average carbon material concentration Ca in the rubber crosslinked product is more than 1 and 8 or less. 4. The sealing material according to any one of claims 1 to 3, which is used in an environment in which it is in close contact with a metal surface. The binary fluororubber is a vinylidene fluoride-hexafluoropropylene copolymer,
The sealing material according to any one of claims 1 to 4, wherein the vinylidene fluoride-hexafluoropropylene copolymer has a fluorine content of 65% by mass or more and 70% by mass or less. The carbon material contains carbon black,
The content of the carbon black in the crosslinkable rubber composition is 5 parts by mass or more and 40 parts by mass or less with respect to 100 parts by mass of the binary fluororubber. sealing material. The sealing material according to any one of claims 1 to 6, wherein the carbon material contained in the crosslinked rubber has a surface area S of 5 (m ² /g) or more. The sealing material according to any one of claims 1 to 7, wherein said carbon nanotubes include single-walled carbon nanotubes. The sealing material according to any one of claims 1 to 8 , wherein the crosslinkable rubber composition further contains an acid acceptor. 10. The sealing material of claim 9 , wherein the acid acceptor comprises magnesium oxide and calcium hydroxide. The rubber crosslinked product has a surface resistivity of 1×10 ⁸ Ω/sq. The sealing material according to any one of claims 1 to 10 , wherein: The sealing material according to any one of claims 1 to 11 , wherein the compression set of said crosslinked rubber after being heated at 250°C for 70 hours is 80% or less.